Removing and replacing fork seals on a Yamaha TTR250

 

DISCLAIMER: The modifications described in the following text are for educational purposes only. In no way do I recommend that you apply these modifications to your own motorcycle. If you do choose to go ahead and modify your motorcycle based on the information in this document you will accept all responsibility for your own actions. The author(s) of this document, and host(s) providing it for you, accept no responsibility whatsoever. If you are unqualified to make any of the changes described herein but are bent on doing the modification, seek out a knowledgeable friend or professional mechanic for assistance.

Removing and replacing fork seals on a Yamaha TTR250

There is quite a lot of work involved and it is essential that you have the workshop manual to hand for full details of the procedures, torque settings, etc.

Before you start, make sure that the bike is safely on a stand and at a comfortable working height - if at all possible.

Buy the correct fork oil seals and, preferably, new dust seals especially if you are not using fork gaiters. Either use OEM or an AllBalls kit.

It is important to check for backwards and forward play and, if there is any, install a bushing kit otherwise the oil seal will quickly fail again.
 

Forks - legend of parts.jpg

It is sometimes difficult to cross reference descriptions in the workshop manual to the real thing so I hope the pic above (open it in a new browser window or save it to your PC/laptop/tablet if you need to enlarge it for clarity) and the legend below will help:

1 - outer fork tube

2 - inner fork tube

3 - Damper rod assembly with rebound spring still attached

4 - damper rod

5 - oil lock piece

6 - base valve

7 - fork spring

8 - cap bolt

9 - spring seats

10 - collar

11 - plain washer

12 - slide metal

13 - piston metal

14 - oil (red) and dust (black) seals - I use AllBalls kits

Push down hard on forks and loosen this 14mm hex nut on the base valve (6) of both forks before dismantling. Access to a "windy" or "rattle" gun will make this job  easier.
3.jpg

Loosen brake caliper bolts and all fork clamp bolts
4.jpg

5.jpg

Pull stanchion down and clamp tight again in lower yoke; this enables you to loosen top stanchion cap bolt (8) without having to disturb handlebars etc (same goes for installing as well )
6.jpg

Unscrew fork top (it isn't under any pressure once you have let the air out from the top valve) and drain oil...messy so have well covered area.
7.jpg

8.jpg

Remove wire clip (snap ring) and then remove dust seal. In case of any doubt, replace the dust seal as well as the oil seal.
9.jpg

10.jpg

That is the oil seal - try to get it out with a seal puller first
11.jpg

If no seal puller then unscrew bottom hex nut that you initially loosened and remove bottom fitting (all one piece ) 
12.jpg

Pull fork leg very firmly a few times until seal and slider come out.. It takes a bit of effort.
13.jpg

Make a homemade plate with a 14mm slot (or use an open end spanner of the same size) to hold top of fork from spring and unbolt fork top.

Remove the old oil and dust seals and clean everything up.

Re-assembly is pretty much a reverse of the above.

First insert the damper rod assembly into the chrome tube stanchion and fit it to the lower fork leg.

You may need to use a punch to tap the slide metal (12) back in place.

Put metal spacer over the slider. This is where the seal will sit. 

Install the base valve and tighten to 55Nm.

Lube new seals and carefully slot and lower down stanchion. Use an old seal packet with a bit of fork oil on to save damaging the seal lips.

Note: the double lip faces down on the red oil seal as shown in pic:

Fork rebuild 009.jpg

Fork rebuild 010.jpg

Use a spare plain washer to put over the seals before tapping them in place with a bit of guttering pipe or similar:

Fork rebuild 010.jpg

This is the part number if you want to buy a section:

Fork rebuild 010.jpg

Next to fit was the retaining spring clip (snap ring). Why aren't they made of stainless steel so they don't rust? (New snap rings are available here when purchased with a repair kit)
Fork rebuild 010.jpg

Top up each leg with 550cc of fork oil of the weight of your choice. 7.5W or 10W will give you a stiffer fork action.

Fork rebuild 016.jpg

Follow the instructions in the manual to pump the damper rod slowly up and down 10 times to distribute the fork oil. Then pump the inner fork tube (2) slowly up and down (no more than 150mm) and wait a few minutes for the air bubbles to disperse - all as per workshop manual.

Now checked the oil level and adjust to 130mm as per manual. To help with this process you can fix a cable tie tightly to a screwdriver shaft.

afork rebuild 018.jpg

It is then a simple job to slowly top up the oil until it just showed on the end of the screwdriver.
afork rebuild 019.jpg

Make sure you have a retaining string or wire on the damper rod so as not to lose it down the tube! Then fit the spring (7), spring seats (9) and collar(10) by threading them over the wire:
Fork rebuild 018.jpg

Having fitted the main fork spring (7), spring seats (9) and collar(10) by threading them over the wire, pull up the damper with the wire and screw on the cap bolt (8) using an open-end spanner on the lock nut.

afork rebuild 020.jpg

It is then a simple job to screw the cap bolt into the inner fork tube (2).

afork rebuild 024.jpg

Job done - TTR up and running :-)
16.jpg

Take your time, allow about 2 hrs :-) 

Good luck! I hope the pics help.

Authors and photographers: Kenny Cox, Wirral, UK and Brian Sussex, Devon, UK.
 

http://www.totallyttrs.com/ - everything you need (possibly!) for your TTR250
http://www.ttr250.com/ - all you ever wanted to know about TTR250s
http://ttr250.activeboard.com/ - the forum for TTR250 owners
http://www.totallywrs.com/ -
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